A storage element array is generally a cooperative arrangement of a plurality of storage elements that are individually, and preferably concurrently, accessible by a client device as if all the storage elements were lumped into one storage unit. The type or types of storage elements used is not limited, permitting the selection of different types of storage elements to leverage the inherent advantages of each under certain operating conditions and/or processing requirements. Typical storage elements include tape cartridges, disk drives, solid state drives, optical drives, semiconductor memory devices generally, and the like, and various combinations thereof.
A tape drive array, for example, includes a plurality of discrete tape drives under common control of an array controller. The array controller virtualizes the totality of the physical storage space afforded by the plurality of tape drives and selectable tape cartridges forming the array, and presents that totality of physical storage capacity to one or more clients in the form of one or more virtual storage spaces.
A tape drive is inherently susceptible to write errors due to defects or even just variations in the recording material of the tape cartridge. The ongoing demand for recording material capable of greater storage density concomitantly increases the adverse effects of these writing errors. That is, writing error rates that could in the past be disregarded as negligible without adversely affecting either quality or performance now must be affirmatively reckoned with. Those errors adversely affect the availability of encrypted data.
A tape library is also inherently susceptible to data accessibility constraints due to the fact that there are more tape cartridges potentially available for use than there are tape drives to write data to and read data from any particular tape cartridge. Handling simultaneous calls for different processes such as high priority access commands in relation to some tape cartridges and other commands in relation to other tape cartridges can problematically choke the data throughput performance of the tape library. The claimed embodiments are directed to improvements resulting from performing encryption command processing from a pool of redundant encrypted data, providing an opportunity to select a set of encrypted data from a corresponding plurality of storage elements that optimizes the totality of the operating performance characteristics in view of other data processing activities and data availability or integrity.